Microencapsulation is a widely utilised process in the pharmaceutical industry for applications in delayed release, sustained release and targeting of administered drugs to their optimum site of absorption and/or action. In addition microencapsulation can be used to mask unpleasant taste and to protect drug from environmental influences such as oxidation or from contact with other incompatible material/actives. A range of techniques exist for microencapsulation, including coacervation, solvent evaporation from emulsions, and fluid bed coating.
Spray drying is among the most efficient and widely used technique for the drying of liquids and slurries. It is reliable, reproducible and is a one-step continuous procedure offering easy scale-up. Spray drying is a technique where a liquid stream is sprayed through a nozzle into a chamber with hot circulating gas such as air, nitrogen or argon. Droplets formed at the nozzle are dried in the hot gas resulting in the formation of particles. The resulting dried material usually is microparticles consisting of a uniform mix of the various components of the spray dried solution as shown in FIG. 1.